I have been trying to set up my full length dies in THE most optimum manner for semi-auto accuracy and dependable feeding. I have two semi-auto's that have been worked on extensively for accuracy at the bench but I believe I am overworking my brass. I purchased a couple of case gages with 'steps' for min and max SAMI (Forester & L.E. Wilson) It would seem that my chambers are pretty snug however as fired cases that have NOT been resized fall right to the Min. SAMI step thus not giving me a benchmark to adjust my FL Die (both in my JP 223 and DPMS 308). My buddy has told me about the RCBS Precision Case Mic that basically dials down to the datum on the shoulder allowing you to set your FL dies .004-.005" down from the length of a fire formed case. Is this the best way to go??
I have used seperate bump and neck dies but would like to use my Redd. die set as it is what I have already. Thanks for your help

Go with the Stoney Point system for measuring. It's handier, more "universal" for several cartridges, and cheaper.

At one time I had all the Precision Mics RCBS makes, but I've sold them all in favor of the Stoney Point. They are nice. I still have two of them in, I believe, 22-250 and .300 Win Mag, that I'd sell cheap. For the retail price of one which only works for the specific caliber, you can get the Stoney Point system for most calibers at the same price.

If one has just one rifle and one die then measuring the case seems superfluous.

Just set the FL die to size the case just enough for reliable operation.